While I have no programing experience, it would probably be helpful if you would ask a question or explain the situation instead of just posting code.

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Don't take life too seriously -- no one gets out alive. Plus, who wants to arrive to the hereafter in pristine condition wearing a suit and tie?
I want to slide in sideways, worn out, used up, hair a mess, clothes tattered, & screaming, "Whooo! What a ride!"
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Yes this isn't very helpful.
Unless your question is those bits in bold but still not very helpful.

The answers are: .value simply gets the value of the element you are looking for.
Why use the age variable? Well technically you don't have to you could just say:
voteable=(document.getElementById("age").value<18) ?"Too young":"Old enough";

But sometimes for readability of code it's a good idea to use variables.

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He who has never failed has never attempted anything worth succeeding at.

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****************************************
Don't take life too seriously -- no one gets out alive. Plus, who wants to arrive to the hereafter in pristine condition wearing a suit and tie?
I want to slide in sideways, worn out, used up, hair a mess, clothes tattered, & screaming, "Whooo! What a ride!"
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